The present disclosure relates to an imaging device, a signal processing method, and a program. In particular, the present disclosure relates to an imaging device, a signal processing method, and a program, in which a signal can be read from an imaging element by applying one of an interlaced read-out process and a progressive read-out process, and a read-out signal is processed according to each scheme.
There are various kinds of imaging elements which are used in an imaging device for capturing color images. For example, many video cameras employ an imaging element which is configured to have a filter arrangement called a complementary color checkered pattern or a color difference line sequence, in which four kinds of color filters of G (Green), Mg (Magenta), Ye (Yellow), and Cy (Cyan) are arranged in a checkered pattern.
The imaging device calculates and outputs color signals, for example, RGB, of each pixel position based on each of the complementary color signals (G, Mg, Ye, Cy) acquired in each pixel position of the imaging element. By using four kinds of complementary color filters of G (Green), Mg (Magenta), Ye (Yellow), and Cy (Cyan), a brightness signal with high sensitivity is advantageously achieved. In particular, such a complementary color filter is widely used in video cameras.
For example, in the related art, Japanese Unexamined Patent Application Publication No. 63-198495 discloses a technique in which color signals such as an RGB signal are obtained using an imaging element having the complementary color filters. In Japanese Unexamined Patent Application Publication No. 63-198495, there is disclosed a configuration that, using a 1H delay element for delaying one horizontal line, the RGB signal is obtained by calculation from both signals Cr(2R−G) and Cb(2B−G) which correspond to a signal of the current line and a signal before one line respectively, and each signal is subjected to a white balance (WB) process, and then a gamma (γ) correction process is performed, so that a color signal which is excellent in color reproducibility is obtained.
However, in such signal processing, since the four kinds of the color filters of G (Green), Mg (Magenta), Ye (Yellow), and Cy (Cyan) have deviation in color characteristic, there is a problem in that the characteristic of the calculated RGB signal varies largely. Therefore, if an additional process, for example, adjusting arithmetic equations individually against the deviation is not performed, the deviation in color reproducibility influences products. Further, in the signal processing method of the related art in which the RGB signal is calculated from both signals Cr(2R−G) and Cb(2B−G) corresponding to the current line and the line before one line respectively and then the color signals are obtained from the RGB signal, there is a problem in that aliasing occurs in a contour in which colors of an subject vary in the vertical direction.
On the other hand, as a method of reading out a signal from an imaging element, a progressive read-out scheme in which pixel data of the imaging element is read as independent signals for all pixels, and an interlaced read-out scheme in which pixels of two lines adjacent in the vertical direction are mixed and read is known. In a video camera of which the format of the output signal from the imaging element is the interlaced scheme, when a frame image in capturing a moving image is taken out as a still image, there is a problem in that blurring is perceptible in the next moving image portion as the interlaced scheme causes a difference of exposure timing of every line.
For this reason, there is proposed a configuration in which the imaging element is operated progressively to obtain an image without blurring when a still image is cut out even in the video camera of which the format of the output signal from the imaging element is the interlaced scheme. However, there is a problem in that when the progressive read-out is performed, the sensitivity is degraded further more than in the case of the interlaced operation, or the data rate at the output of the imaging element is increased such that power consumption ascends.
As a technique which discloses a signal processing method, there are, for example, Japanese Unexamined Patent Application Publication No. 11-98515 and Japanese Patent No. 3483732. In the technique, the interlaced read-out and the progressive read-out of the imaging element are configured to be switchable, and furthermore brightness/color signals are generated according to the read-out scheme. However, including these techniques, in the erstwhile related art, there is no disclosure in which the respective characteristics of the brightness signal and the color signal are approximated to each other when the interlaced read-out and the progressive read-out are switched to be used. Therefore, among images of different read-out schemes, there is a problem in that a difference between the characteristics of the brightness signal and the color signal is generated. The current state is that the problem has not been solved.